Chocolate Snowswirl Fudge

3 cups (18 ounces) semisweet chocolate chips
1 (14 ounce) can chocolate or original sweetened condensed milk
4 tablespoons butter or margarine
1 1/2 teaspoons vanilla extract
Dash of salt
1 cup chopped nuts
2 cups miniature marshmallows

Melt chips with sweetened condensed milk, 2 tablespoons of the butter, vanilla extract and salt. Remove from heat; stir in nuts. Spread evenly into foil-lined 8- or 9-inch square pan. Melt marshmallows with remaining 2 tablespoons butter. Spread on top of fudge. With table knife or metal spatula, swirl through top of fudge. Chill at least 2 hours or until firm.

Turn fudge onto cutting board; peel off foil and cut into squares. Store loosely covered at room temperature.